The present invention relates generally to an aqueous base lubricant, and more specifically to a lubricant for the high temperature application upon surfaces of a glass shear, or otherwise upon relatively movable metallic surfaces at high temperature. The lubricant contains a substantial quantity of coconut oil together with an alkanolamine, the phosphate ester of a linear primary alcohol, an emulsifier, a primary amine and a wetting agent. The lubricant formulation of the present invention is usable at modest concentrations, hence rendering the material cost effective, and furthermore reducing any unusual load on sewage treatment facilities.
The present invention was specifically designed to accommodate certain unique requirements of the glass industry. In the process of making glass containers, a cylinder of molten glass is extruded and cut by shear blades into a "gob". The molten glass gob then leads into the mold chamber by sliding down a loading chute. The molten glass is highly abrasive to both the shear blades and loading chute. A mixture of water and a lubricant is sprayed onto the shear blades and loading chute to assure a continuation of efficient and precise shear cuts and loading times.
It is necessary therefore for the efficient production of quality glassware, that the following conditions be met:
1. Lubricity must be adequate for the continuous protection of the shear blades and loading chute. PA1 2. Corrosion inhibition is necessary for the protection of all surfaces which come into contact with the aqueous lubricating solution. PA1 3. The lubricant must be composed of non-drying components such that a hard film does not form or is otherwise built-up on shear blades resulting in poor heat transfer and inefficient gob cuts. PA1 4. The lubricant must be able to provide lubrication at minimal concentrations in water to produce maximum cooling benefits. PA1 5. The lubricant must provide good surface wetting characteristics in order to assure efficient heat transfer at the shear blades. PA1 6. The lubricant must be biodegradable since essentially all shear lubrication systems are based upon a once-through, non-recirculating system with the spent lubricant solution entering municipal water treatment facilities.
Since the temperature of the molten glass in contact with the shear blades is normally in the vicinity of 2000.degree. F., cooling of the shear blades is a primary concern. Generally speaking, the lubricants best suited for cooling efficiency are the water-based lubricants.
Since lubrication of the shear blades and loading chute is necessary for the production of high quality glassware and since a lubricating film must be present a high water-to-lubricant dilution, the lubricant must possess excellent lubrication properties. Generally speaking, the compounds offering the best lubricity are oil-based lubricants.
The present invention combines the best properties of soluble oil lubricants and water-based lubricants. In other words, the invention is considered to be a hybrid of oil-based and synthetic lubricants; thus a semi-synthetic. The definition of semi-synthetic is essentially a compound containing oil in which the oil component comprises less than 50% by weight of the total non-aqueous component fractions of the formulation. Water, therefore, may be present in a semi-synthetic product but normally is not considered when computing the percentage of oil present in the formulation.
The importance of lower levels of oil can be appreciated by considering the problems of pollution in a once-through system wherein the spent lubricant is discharged into the environment. While animal and vegetable oils are considered biodegradable, their BOD values are high enough to warrant efforts to decrease the amount discharged into the environment or into municipal sewage systems. Often municipalities impose surcharges on the sewage treatment rates of a manufacturing or commercial facility dependent on the BOD or COD of their effluent.
The present invention therefore provides a lubricant having lubricating properties essentially equal to those of the soluble oil products at equal or greater dilutions while reducing the amount of oil used in the process.
The primary lubricant component of the invention is the non-drying vegetable oil, with coconut oil being preferred. The alkanolamine, methyl ester and phosphate ester are lubricant additives. The function of the lubricant additives is to lower the percentage of oil necessary to maintain efficient lubrication, with the methyl ester functioning as a primary wetting agent. Additionally, the methyl ester provides secondary emulsion stability. The emulsifier system is composed of an ethyoxylated sorbitol hexaoleate. Secondary emulsion stability is also provided by the primary amine and phosphate ester. Corrosion inhibition is afforded to the product by the alkanolamine, primary amine and phosphate ester. Bacterial degradation and rancidity are inhibited by the primary amine.